Psittacosis -- also known as parrot disease, parrot fever,
and ornithosis -- can cause severe pneumonia and other serious
health problems among humans. Approximately 800 cases of
psittacosis (infection with Chlamydia psittaci) were reported to
CDC from 1987 through 1996, and most resulted from exposure to pet
birds, usually parrots, macaws, cockatiels, and parakeets. In
birds, C. psittaci infection is referred to as avian chlamydiosis
(AC). Infected birds shed the bacteria through feces and nasal
discharges, which can remain infectious for several months. This
compendium provides information about psittacosis and AC to public
health officials, physicians, veterinarians, members of the pet
bird industry, and others concerned about controlling these
diseases and protecting public health. The recommendations in this
compendium provide effective, standardized procedures for
controlling AC in birds, a vital step to protecting human health.

INTRODUCTION

Chlamydia psittaci is a bacterium that can be transmitted
from pet birds to humans. In humans, the resulting infection is
referred to as psittacosis (also known as parrot disease, parrot
fever, and ornithosis). Psittacosis often causes influenza-like
symptoms and can lead to severe pneumonia and nonrespiratory
health problems. With proper treatment, the disease is rarely
fatal. From 1987 through 1996, CDC received reports of 831 cases
of psittacosis (1), which is an underestimate of the actual number
of cases because psittacosis is difficult to diagnose.

During the 1980s, approximately 70% of the psittacosis cases
with a known source of infection resulted from human exposure to
caged pet birds; of these persons, the largest group affected
(43%) included bird fanciers and owners of pet birds. Pet shop
employees accounted for an additional 10% of cases. Other persons
at risk include pigeon fanciers and persons whose occupation
places them at risk for exposure (e.g., employees in poultry
slaughtering and processing plants, veterinarians, veterinary
technicians, laboratory workers, workers in avian quarantine
stations, farmers, and zoo workers). Because human infection can
result from brief, passing exposure to infected birds or their
contaminated droppings, persons with no identified leisure-time or
occupational risk can become infected.

In this report, C. psittaci infection in birds is referred to
as avian chlamydiosis (AC). The bacterium C. psittaci has been
isolated from approximately 100 bird species and is most commonly
identified in psittacine birds such as parrots, macaws,
cockatiels, and parakeets. Among caged, nonpsittacine birds,
infection with C. psittaci occurs most frequently in pigeons,
doves, and mynah birds. The incidence of infection in canaries and
finches is believed to be lower than in other psittacine birds.

The recommendations in this compendium provide effective,
standardized procedures for controlling AC in the pet bird
population, an essential step in efforts to control psittacosis
among humans. This compendium is intended to guide public health
officials, physicians, veterinarians, persons in the pet bird
industry, and others concerned with the control of C. psittaci
infection and the protection of public health.

PART I. INFECTION AMONG HUMANS (PSITTACOSIS)
Transmission

Because several diseases affecting humans can be caused by
other species of Chlamydia, the disease resulting from the
infection of humans with C. psittaci frequently is referred to as
psittacosis rather than chlamydia. Most C. psittaci infections in
humans result from exposure to pet psittacine birds. Infection
with C. psittaci usually occurs when a person inhales the
organism, which has been aerosolized from respiratory secretions
or dried feces of infected birds. Other means of exposure include
bird bites, mouth-to-beak contact, and the handling of infected
birds' plumage and tissues. Even brief exposures can lead to
symptomatic infection; therefore, some patients with psittacosis
may not recall or report having any contact with birds.

Mammals occasionally transmit C. psittaci to humans. Certain
strains of C. psittaciinfect sheep, goats, and cattle, causing
chronic infection of the reproductive tract, placental
insufficiency, and abortion in these animals. These strains of C.
psittaci are transmitted to persons when they are exposed to the
birth fluids and placentas of infected animals. Another strain of
C. psittaci, feline keratoconjunctivitis agent, typically causes
rhinitis and conjunctivitis in cats. Transmission of this strain
from cats to humans appears to occur rarely.

Human-to-human transmission has been suggested but not
proven. Standard infection-control precautions are sufficient for
patients with psittacosis, and specific isolation procedures
(e.g., a private room, negative pressure air flow, and masks) are
not indicated.

Clinical Signs and Symptoms

For persons infected with C. psittaci, the onset of illness
follows an incubation period of 5-14 days. The severity of this
disease ranges from inapparent illness to systemic illness with
severe pneumonia. Before antimicrobial agents were available,
15%-20%
of persons with C. psittaci infection were reported to have
died. However, less than 1% of properly treated patients now die
as a result of the infection.

Persons with symptomatic infection typically have abrupt
onset of fever, chills, headache, malaise, and myalgia. They
usually develop a nonproductive cough that can be accompanied by
breathing difficulty and chest tightness. A pulse-temperature
dissociation (fever without elevated pulse), enlarged spleen, and
rash are sometimes observed and suggest a diagnosis of psittacosis
for patients with community-acquired pneumonia. Auscultatory
findings may underestimate the extent of pulmonary involvement.
Radiographic findings include lobar or interstitial infiltrates.
The differential diagnosis of psittacosis-related pneumonia
includes infection with Coxiella burnetii, Mycoplasma pneumoniae,
Chlamydia pneumoniae, Legionella species, and respiratory viruses
such as influenza. C. psittaci can affect organ systems other than
the respiratory tract and result in endocarditis, myocarditis,
hepatitis, arthritis, keratoconjunctivitis, and encephalitis.
Severe illness with respiratory failure, thrombocytopenia,
hepatitis, and fetal death has been reported among pregnant women.

Diagnosis

A patient is considered to have a confirmed case of
psittacosis if clinical illness is compatible with psittacosis and
the case is laboratory confirmed by one of three methods: a) C.
psittaci is cultured from respiratory secretions; b) antibody
against C. psittaci is increased by fourfold or greater (to a
reciprocal titer of greater than or equal to 32 between paired
acute- and convalescent-phase serum specimens collected at least
2 weeks apart) as demonstrated by complement fixation (CF) or
microimmunofluorescence (MIF); or c) immunoglobulin M antibody
against C. psittaci is detected by MIF (to a reciprocal titer of
greater than or equal to 16). A patient is considered to have a
probable case of psittacosis if clinical illness is compatible
with psittacosis and a) the case is epidemiologically linked to a
confirmed case of psittacosis or b) a single antibody titer
greater than or equal to 32, demonstrated by CF or MIF, is present
in at least one serum specimen obtained after onset of symptoms.
CDC and the Council of State and Territorial Epidemiologists
established these case definitions for epidemiologic purposes (2).
These definitions should not be used as the sole criteria for
establishing clinical diagnoses.

Until recently, the diagnosis almost always was established
by using serologic methods in which paired sera were tested for
Chlamydia antibodies by CF test. However, because Chlamydia CF
antibody is not species-specific, high CF titers also may result
from Chlamydia pneumoniae and Chlamydia trachomatis infection.
Acute-phase serum specimens should be obtained as soon as possible
after the onset of symptoms, and convalescent-phase serum
specimens should be obtained greater than or equal to 2 weeks
after the onset of symptoms. Because treatment with tetracycline
can delay or diminish the antibody response, a third serum sample
might help confirm the diagnosis. All sera should be tested
simultaneously at the same laboratory. If the patient's
epidemiologic and clinical history indicate a possible diagnosis
of psittacosis, MIF assays can be used to distinguish C. psittaci
infection from infection with other chlamydial species.
Information about laboratory testing often is available at state
laboratories. The infectious agent also can be isolated from the
patient's sputum, pleural fluid, or clotted blood during acute
illness and before treatment with antimicrobial agents; however,
culture of C. psittaci is performed by few laboratories because of
technical difficulty and safety concerns.

Treatment

Tetracyclines are the drugs of choice for treating patients
with psittacosis. Most persons respond to oral therapy (100 mg of
doxycycline administered twice a day or 500 mg of tetracycline
hydrochloride administered four times a day). For initial
treatment of severely ill patients, doxycycline hyclate may be
administered intravenously at a dosage of 4.4 mg/kg (2 mg/lb) body
weight per day divided into two infusions per day (up to 100 mg
per dose). In past years, tetracycline hydrochloride has been
administered to patients intravenously (10-15 mg/kg body weight
per day divided into four doses per day), but a preparation for
injection is no longer available in the United States. Remission
of symptoms usually is evident within 48-72 hours. However,
relapse can occur, and treatment must continue for at least 10-14
days after fever abates. Although its in vivo efficacy has not
been determined, erythromycin probably is the best alternative
agent for persons for whom tetracycline is contraindicated (e.g.,
children aged less than 9 years and pregnant women).

PART II. INFECTION AMONG BIRDS (AVIAN CHLAMYDIOSIS)
Transmission

Shedding of the infectious agent among birds with latent
chlamydiosis may be activated by several stress factors, including
shipping, crowding, chilling, and breeding. Birds can appear
healthy but be carriers of C. psittaci and can shed the organism
intermittently. When shedding occurs, the organism is excreted in
the feces and nasal discharges of infected birds. The organism is
resistant to drying and can remain infectious for several months.

Clinical Signs

For caged birds, the time between exposure to C. psittaci and
the onset of illness ranges from 3 days to several weeks. However,
latent infections are common among birds, and active disease may
appear years after exposure. C. psittaci infection in birds can be
asymptomatic or can result in an acute, subacute, or chronic
clinical disease. Whether the bird exhibits clinical signs of
illness or dies depends on the species of bird, virulence of the
strain, infectious dose, stress factors, age, and extent of
treatment or prophylaxis.

Birds with clinical signs of AC typically have manifestations
(e.g., lethargy, anorexia, and ruffled feathers) consistent with
those of other systemic illnesses. Other signs associated with AC
include serous or mucopurulent ocular or nasal discharge,
diarrhea, and excretion of green to yellow-green urates. Anorectic
birds may produce sparse, dark green droppings. Birds can die soon
after onset of illness or, as the disease progresses, can become
emaciated and dehydrated before death.

Diagnosis

Several diagnostic methods are available for identifying AC
in birds (Appendix A). A confirmed case of AC is defined as
infection with C. psittaci on the basis of at least one of the
following laboratory results: a) isolation of C. psittaci from a
clinical specimen, b) identification of chlamydial antigen by
immunofluorescence (fluorescent antibody {FA}) of the bird's
tissues, c) a greater than fourfold change in serologic titer in
two specimens from the bird obtained at least 2 weeks apart and
assayed simultaneously at the same laboratory, or d)
identification of C. psittaci within macrophages in smears stained
with Gimenez or Macchiavellos stain or sections of the bird's
tissues.

A probable case of AC is defined as C. psittaci infection in
a bird that has clinical illness compatible with AC and at least
one of the following laboratory results: a) a single high
serologic titer in one or more specimens obtained after the onset
of signs or b) the presence of C. psittaci antigen (identified by
enzyme-linked immunosorbent assay {ELISA} or FA) in feces, a
cloacal swab, or respiratory or ocular exudates.

A suspected case of AC is defined as a) clinical illness
compatible with AC that is epidemiologically linked to another
case in a human or bird but that is not laboratory confirmed, b)
an asymptomatic infection in a bird with a single high serologic
titer or detection of chlamydial antigen, c) illness in a bird
that has positive results for infection on the basis of a
nonstandardized test or a new investigational test, or d) a
clinical illness compatible with chlamydiosis that is responsive
to appropriate therapy.

Treatment

Veterinarians can choose from three types of methods for
treating birds with AC -- medicated feed (chlortetracycline), oral
or parenteral treatment (doxycycline or oxytetracycline), and
experimental treatment (fluoroquinolones, late-generation
macrolides, pharmacist-compounded injectable doxycycline, and
doxycycline-medicated feed) (Appendix B). Although these protocols
are usually successful, knowledge about AC treatment is evolving,
and no treatment protocol guarantees safe treatment or complete
elimination of infection by the etiologic agent C. psittaci in all
bird species. Therefore, treatment should be supervised by a
licensed veterinarian.

PART III. RECOMMENDATIONS AND REQUIREMENTS
Recommendations for Controlling Infection Among Humans and Birds

To prevent the transmission of C. psittaci to persons and
other birds, the following control measures are recommended for
physicians, veterinarians and their staffs, and members of the pet
bird industry:

Take measures to protect persons at high risk from becoming
infected. All persons in contact with infected birds should be
informed about the nature of the disease. If a person who has
been
exposed develops respiratory illness, the physician should
initiate early and specific treatment for psittacosis. Persons
at
risk should be instructed to wear protective clothing, gloves, a
paper surgical cap, and a respirator with an N95 rating or a
higher-efficiency respirator when cleaning cages or handling
infected birds. Surgical masks may not be effective in
preventing
transmission of C. psittaci. When necropsies are performed on
potentially infected birds, additional precautions should be
taken, including a) wetting the carcass with detergent and water
to prevent aerosolization of infectious particles and b) working
under an examining hood that has an exhaust fan.

Maintain accurate records of all bird-related transactions to
aid in identifying sources of infected birds and potentially
exposed persons. Records should include the date of purchase,
species of birds purchased, source of birds, and any identified
illnesses or deaths among birds. In addition, when birds are
sold
by a store, the seller should record the name, address, and
telephone number of the customer; the date of purchase; the
species of birds purchased; and the band numbers if applicable.

Do not purchase or sell birds that have signs of AC (e.g.,
ocular or nasal discharge, diarrhea, or low body weight).

Quarantine newly acquired birds for 30-45 days, and test or
prophylactically treat them before adding them to a group.

Consider birds that have been to shows, exhibitions, fairs, and
other events as newly acquired birds, and quarantine them upon
return to the facility.

Test birds for AC before they are to be boarded or sold on
consignment, and house them in a room separate from other birds.

Practice preventive husbandry. Position cages to prevent the
transfer of fecal matter, feathers, food, and other materials
from
one cage to another. Do not stack cages, and be sure to use
solid-sided cages or barriers if cages are adjoining. The bottom
of the cage should be made of wire mesh, and litter that will
not
produce dust (e.g., newspapers) should be placed underneath the
mesh. Clean all cages and food and water bowls daily. Soiled
bowls
should be emptied, cleaned with soap and water, rinsed, placed
in
a disinfectant solution, and rinsed again before reuse. Between
occupancies by different birds, cages should be thoroughly
scrubbed with soap and water, disinfected, and rinsed in clean,
running water. Exhaust ventilation should be sufficient to
prevent
accumulation of aerosols.

Prevent the spread of infection. If AC is confirmed, probable,
or suspected, birds requiring treatment should be held in
isolation. Rooms and cages where infected birds were housed
should
be cleaned immediately and disinfected thoroughly to eliminate
chlamydial organisms from the environment. When the cage is
being
cleaned, transfer the bird to a clean cage. Thoroughly scrub the
soiled cage with a detergent to remove all fecal debris, rinse
the
cage, disinfect it (allowing at least 5 minutes of contact with
the disinfectant), and rerinse the cage to remove the
disinfectant. Discard all items that cannot be adequately
disinfected (e.g., wooden perches, nest material, and litter).
While birds are being treated, minimize the circulation of
feathers and dust by taking precautions such as wet-mopping the
floor frequently with disinfectants and preventing air currents
and drafts within the area. Reduce contamination from dust by
spraying the floor with a disinfectant or water before sweeping
it. Do not use a vacuum cleaner, because vacuuming can cause
aerosolization of infectious particles. Frequently remove waste
material from the cage (after moistening the material), and burn
or double-bag the waste for disposal. When possible, care for
healthy birds before handling isolated birds.

Use disinfection measures. Because C. psittaci has a high lipid
content, it is susceptible to most disinfectants and detergents.
In the clinic or laboratory, a 1:1,000 dilution of quaternary
ammonium compounds (e.g., Roccal or Zephiran ) is effective, as
is 70% isopropyl alcohol, 1% Lysol , 1:100 dilution of household
bleach (i.e., 2.5 tablespoons per gallon {10 mL/L}), or
chlorophenols. (C. psittaci is susceptible to heat but is
resistant to acid and alkali.) Many disinfectants are
respiratory
irritants and should be used in a well-ventilated area. Avoid
mixing disinfectants with any other product.

Recommendations for Treating and Caring for Infected Birds

All birds with confirmed or probable AC should be isolated
and treated, preferably under the supervision of a veterinarian
(Appendix B). Birds with suspected AC or birds previously exposed
to AC should be isolated and retested or treated. Because treated
birds can be reinfected with C. psittaci after treatment, such
birds should not be exposed to untreated birds or other potential
sources of infection. To prevent reinfection from environmental
sources, aviaries should be thoroughly cleaned and sanitized. No
vaccine against chlamydiosis in birds is available.

The following general recommendations should be followed by
bird owners and dealers when treating and caring for birds with
confirmed, probable, or suspected cases of AC:

Protect birds from undue stress (e.g., chilling or shipping),
poor husbandry, or malnutrition. These problems reduce the
effectiveness of treatment and promote the development of
secondary infections with other bacteria or yeast.

Observe the birds daily, and weigh them every 3-7 days. If the
birds are not maintaining weight, have them reevaluated by a
veterinarian.

Do not administer antimicrobial agents to birds through
drinking water, and avoid the use of high dietary concentrations
of calcium or other divalent cations.

Isolate birds that are to be treated in clean, uncrowded cages,
segregated by sex.

Clean up all spilled food promptly; wash food and water
containers daily.

Provide fresh water and appropriate vitamins daily.

Continue medication for the full treatment period to avoid
relapses. Birds may appear clinically improved and have reduced
shedding after 1 week.

Responsibilities of Veterinarians and Physicians

Veterinarians should be aware that AC is not a rare disease
among pet birds and should consider a diagnosis of AC for any
lethargic bird that has nonspecific signs of illness, especially
if the bird was purchased recently. If AC is suspected, the
veterinarian should submit appropriate laboratory specimens to a
veterinary diagnostic laboratory to confirm the diagnosis. Both
laboratories and attending veterinarians should follow local and
state regulations or guidelines regarding case reporting.
Veterinarians should work closely with authorities who conduct
investigations in their jurisdictions. When appropriate,
veterinarians should inform clients that infected birds should be
isolated and treated. In addition, they should educate clients
about the public health hazard posed by AC and the appropriate
precautions that should be taken to avoid the risk for
transmission. Persons exposed to the birds should seek medical
attention if they develop influenza-like symptoms or other
respiratory illness.

Most states require physicians to report cases of psittacosis
among humans to the appropriate health authorities. Timely
diagnosis and reporting may help identify the source of infection
and control the spread of disease. Because single-serum titers are
both insensitive and nonspecific for diagnosis of psittacosis,
confirmation with paired acute- and convalescent-phase sera is
recommended. Birds that are suspected sources of human infection
should be referred to veterinarians for evaluation and treatment.
Local and state authorities may conduct epidemiologic
investigations and institute additional disease-control measures
(see Local and State Epidemiologic Investigations).

Quarantine of Birds

The appropriate animal and public health authorities may
issue a quarantine for all affected and susceptible birds on a
premises where C. psittaci infection has been identified. The
purpose of imposing a quarantine is not to discourage disease
reporting but to prevent further disease transmission (3). Because
of the severe economic impact of quarantines, reasonable economic
options should be made available to the owners and operators of
pet stores. For example, with the approval of state or local
authorities, the owner of quarantined birds may choose to a) treat
the birds in a separate quarantine area to prevent exposure to the
public and other birds or b) euthanize the infected birds. After
completion of the treatment or removal of the birds, a quarantine
can be lifted when the infected premises are thoroughly cleaned
and disinfected. The area can then be restocked with birds.

Bird Importation Regulations

The Veterinary Services of the Animal and Plant Health
Inspection Service, U.S. Department of Agriculture (USDA),
regulates the importation of pet birds to ensure that exotic
poultry diseases are not introduced into the United States. These
regulations are set forth in the Code of Federal Regulations,
Title 9, Chapter 1 (3). Because of the possibility of smuggled pet
birds, these import measures do not guarantee that AC cannot enter
the United States. In general, current USDA regulations regarding
the importation of birds include the following requirements:

Before shipping the birds, the importer must obtain an import
permit from the USDA and a health certificate issued and/or
endorsed by a veterinarian of the national government of the
exporting country.

A USDA veterinary inspection must be conducted at the first
port of entry in the United States and a quarantine be imposed
for
a minimum of 30 days at a USDA-approved facility, to determine
whether the birds are free of evidence of communicable diseases
of
poultry. In addition, the birds must be tested to ensure they
are
free of exotic Newcastle disease and pathogenic avian influenza.

During the 30-day U.S. quarantine, psittacine birds must
receive a balanced, medicated feed ration containing greater
than
or equal to 1% chlortetracycline (CTC) with less than or equal
to
0.7% calcium for the entire quarantine period as a precautionary
measure against AC. The USDA recommends that importers continue
CTC prophylactic treatment of psittacine birds for an additional
15 days (i.e., for 45 continuous days).

Local and State Epidemiologic Investigations

Public health or animal health authorities at the local or
state level may need to conduct epidemiologic investigations to
help control the transmission of C. psittaci to humans and birds.
An epidemiologic investigation should be initiated if a) a bird
with confirmed or probable AC was procured from a pet store,
breeder, or dealer within 60 days of the onset of signs of
illness, b) a person has confirmed or probable psittacosis, or c)
several suspect avian cases have been identified from the same
source. Other situations may be investigated at the discretion of
the appropriate local or state public health departments or animal
health authorities.

Investigations involving recently purchased birds should
include a visit to the site where the infected bird is located and
identification of the location where the bird was originally
procured (e.g., pet shop, dealer, breeder, or quarantine station).
During such investigations, authorities should consider
documenting the number and types of birds involved, the health
status of potentially affected persons and birds, locations of
facilities where birds were housed, relevant ventilation-related
factors, the treatment protocol, and the source of medicated feed,
if such treatment is initiated. To help identify multistate
outbreaks of C. psittaci infection, local and state authorities
should report suspected outbreaks to the Respiratory Diseases
Branch, Division of Bacterial and Mycotic Diseases, National
Center for Infectious Diseases, CDC, telephone (404) 639-2215.

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